Recent decades have seen much scientific effort directed to the study and treatment of various cardiac arrhythmias, both lethal and non-lethal. Many patients have benefited from these efforts. For example, it is well known that atrial and ventricular tachycardias and fibrillation can be reversed by appropriate electrical stimulation or cardioversion. Unfortunately, the necessary equipment is often available only in a sophisticated medical environment. Thus, those individuals who experience a cardiac arrhythmia that culminates in ventricular fibrillation too often do not have the benefit of this technology. More than one half of the deaths from coronary heart disease occur suddenly, outside the hospital, with the majority being believed to result from a disturbance in cardiac electrical activity which culminates in ventricular fibrillation.
To counter the situation described above, automatic cardiac defibrillators have been proposed. Examples of such devices are disclosed in U.S. Pat. No. 3,614,954 for Electronic Standby Defibrillator in the name of Mirowski et al. and U.S. Pat. No. 3,614,955 for Standby Defibrillator and Method of Operation in the name of Mirowski, both issued Oct. 26, 1971. While studies of such systems are encouraging, they nonetheless require high voltages (1,000 volts) and large energies (45 joules). Such large voltage and energy levels produce severe pain which requires that the patient enter a severely hypodynamic state resulting in a loss of consciousness before the therapy is initiated. Also because of the high levels, an improperly applied therapeutic shock may itself result in fibrillation. In addition, a device malfunction delivering a shock to a non-fibrillating heart would, at best, be very uncomfortable and is potentially dangerous.